Multi-pump control system with power consumption optimization

Abstract

A multi-pump control system includes a control module, a processing module, a communication interface, and a storage module. The control module runs n different subsets of i pumps of a multi-pump system including N pumps during n different configuration cycles at a speed .sub.j, wherein N2, 2n2.sup.N1 and 1iN. Each configuration cycle j{1, . . . , n} is associated with a subset j{1, . . . , n} and a speed .sub.j. The communication interface receives signals indicative of operational parameters from each subset j during the associated configuration cycle j. The processing module determines an approximated pump characteristic p=f(q, .sub.j) based on the received signals for each subset j and under an assumption that the i pumps of each subset j share the same part q/i of a reference flow q. The storage module stores the approximated pump characteristic p=f(q, .sub.j) or parameters indicative thereof.

Claims

1. A multi-pump control system comprising: a processing module; a communication interface; a storage module; and a control module configured to run n different subsets of i pumps of a multi-pump system comprising N pumps during n different configuration cycles at a speed .sub.j, wherein N2, 2n2.sup.N1 and 1iN, wherein each configuration cycle j{1, . . . , n} is associated with a subset j{1, . . . , n} and a speed .sub.j, wherein the communication interface is configured to receive signals indicative of operational parameters from each subset j during the associated configuration cycle j, wherein the processing module is configured to determine an approximated pump characteristic p=f(q, .sub.j) based on the received signals for each subset j and under an assumption that the i pumps of each subset j share the same part q/i of a reference flow q, and wherein the storage module is configured to store the approximated pump characteristic p=f(q, .sub.j) or parameters indicative thereof.

2. The multi-pump control system according to claim 1, wherein: the processing module is configured to determine an approximated pump power consumption P=f(q, .sub.j) based on the received signals for each subset j and under the assumption that the i pumps of each subset j share the same part q/i of the reference flow q; and the storage module is configured to store the approximated power consumption P=f(q, .sub.j) or parameters indicative thereof.

3. The multi-pump control system according to claim 2, wherein the processing module is configured to determine an approximated power consumption P=f(q, .sub.j) by determining parameters x, y and z of a second order polynomial $P (q,_{j}) = {x (\frac{q}{i})}^{2}_{j} + y (\frac{q}{i})_{j}^{2} + z_{j}^{3} .$

4. The multi-pump control system according to claim 1, wherein the processing module is configured to determine a subset k with a least power consumption for a required load based on an approximated power consumption P=f(q, .sub.j) or an approximated pump characteristic p=f(q, .sub.j) stored in the storage module or based on an approximated power consumption P=f(q, .sub.j) and an approximated pump characteristic p=f(q, .sub.j) stored in the storage module.

5. The multi-pump control system according to claim 4, wherein the control module is further configured to operate the multi-pump system with the determined subset k having the least power consumption for a required load.

6. The multi-pump control system according to claim 1, wherein the control module is configured to run the i pumps of a subset j with the same speed .sub.j during a configuration cycle j, wherein the speed .sub.j of the i pumps of subset j in configuration cycle j differs from the speed Wk of s pumps of a subset kin another configuration cycle k, wherein js, wherein a total head p generated by the multi-pump system 3 is substantially the same for both configuration cycles j, k.

7. The multi-pump control system according to claim 1, wherein the processing module is configured to determine an approximated pump characteristic p=f(q, .sub.j) by determining parameters a, b and c of a second order polynomial $p (q,_{j}) = {a (\frac{q}{i})}^{2} + b (\frac{q}{i})_{j} + c_{j}^{2} .$

8. The multi-pump control system according to claim 7, wherein the processing module is configured to determine the approximated pump characteristic p=f(q, .sub.j) or a power consumption P=f(q, .sub.j) by a least squares method if a number of configuration cycles is equal to or exceeds a number of parameters to be determined.

9. The multi-pump control system according to claim 1, wherein the control module is further configured to: run a zero flow configuration cycle by ramping up the speed of at least one pump in addition to a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump starting to contribute to a total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-up pump in the moment it starts to contribute to the total flow; or run a zero flow configuration cycle by ramping down the speed of at least one pump of a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump stopping to contribute to the total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-down pump in the moment it stops to contribute to the total flow; or run a zero flow configuration cycle by ramping up the speed of at least one pump in addition to a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump starting to contribute to the total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-up pump in the moment it starts to contribute to the total flow and run a zero flow configuration cycle by ramping down the speed of at least one pump of a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump stopping to contribute to the total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-down pump in the moment it stops to contribute to the total flow; and wherein the processing module is configured to identify the received signal change by using a change detection algorithm.

10. The multi-pump control system according to claim 1, wherein the control module is further configured to: run a zero flow configuration cycle by ramping up the speed of at least one pump in addition to a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump starting to contribute to a total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-up pump in the moment it starts to contribute to the total flow; or run a zero flow configuration cycle by ramping down the speed of at least one pump of a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump stopping to contribute to the total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-down pump in the moment it stops to contribute to the total flow; or run a zero flow configuration cycle by ramping up the speed of at least one pump in addition to a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump starting to contribute to the total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-up pump in the moment it starts to contribute to the total flow and run a zero flow configuration cycle by ramping down the speed of at least one pump of a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump stopping to contribute to the total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-down pump in the moment it stops to contribute to the total flow; and wherein the processing module is configured to identify the received signal change by determining if an absolute value of the gradient in p, speed .sub.j, and/or power consumption P is equal to or exceeds a predetermined threshold value.

11. The multi-pump control system according to claim 1, wherein the control module is further configured to: ramp up the speed of k pumps in addition to a subset j of i pumps of a multi-pump system comprising N pumps and running at a speed .sub.j providing a total head p, wherein N2, 1k<N and 1i<N, wherein the control module is configured to ramp down the i pumps of the subset j from the speed .sub.j to a lower speed .sub.m, wherein the speed .sub.m is the speed required for a subset m of i+k pumps to provide the total head p; or ramp down the speed of k pumps of a subset j of i pumps of a multi-pump system comprising N pumps and running at a speed .sub.j providing a total head p, wherein N2, 1k<i and 1<iN, wherein the control module is configured to ramp up the i-k pumps of a residual subset r from the speed .sub.j to a higher speed .sub.m, wherein the speed co r is the speed required for a residual subset r of i-k pumps to provide the total head p; or ramp up the speed of k pumps in addition to a subset j of i pumps of a multi-pump system comprising N pumps and running at a speed .sub.j providing a total head p, wherein N2, 1k<N and 1i<N, wherein the control module is configured to ramp down the i pumps of the subset j from the speed .sub.j to a lower speed .sub.m, wherein the speed .sub.m is the speed required for a subset m of i+k pumps to provide the total head p; and ramp down the speed of k pumps of a subset j of i pumps of a multi-pump system comprising N pumps and running at a speed .sub.j providing a total head p, wherein N2, 1k<i and 1<iN, wherein the control module is configured to ramp up the i-k pumps of a residual subset r from the speed .sub.j to a higher speed .sub.r, wherein the speed .sub.r is the speed required for a residual subset r of i-k pumps to provide the total head p.

12. The multi-pump control system according to claim 11, wherein the control module is further configured to keep the total head p constant while ramping up or ramping down.

13. The multi-pump control system according to claim 11, wherein the control module is configured to ramp up or ramp down following at least one pre-determined model curve.

14. A method for controlling a multi-pump system, the method comprising the steps of: running n different subsets of i pumps of the multi-pump system comprising N pumps during n different configuration cycles at a speed .sub.j, wherein N2, 2n2.sup.N1 and 1iN, wherein each configuration cycle j{1, . . . , n} is associated with a subset j{1, . . . , n} and a speed .sub.j; receiving signals indicative of operational parameters from each subset j during the associated configuration cycle j; determining an approximated pump characteristic p=f(q, .sub.j) based on the received signals for each subset j and under an assumption that the i pumps of each subset j share the same part q/i of a reference flow q; and storing the approximated pump characteristic p=f(q, .sub.j) or parameters indicative thereof.

15. The method according to claim 14, further comprising determining an approximated pump power consumption P=f(q, .sub.j) based on the received signals for each subset j and under the assumption that the i pumps of each subset j share the same part q/i of the reference flow q, and storing the approximated power consumption P=f(q, .sub.j) or parameters indicative thereof.

16. The method according to claim 15, further comprising determining the approximated power consumption P=f(q, .sub.j) by determining parameters x, y and z of a second order polynomial $P (q,_{j}) = {x (\frac{q}{i})}^{2}_{j} + y (\frac{q}{i})_{j}^{2} + z_{j}^{3},$ wherein .sub.j is the speed of the i pumps of a subset j.

17. The method according to claim 15, further comprising determining the approximated pump characteristic p=f(q, .sub.j) or power consumption P=f(q, .sub.j) by a least squares method if a number of configuration cycles is equal to or exceeds a number of parameters to be determined.

18. The method according to claim 14, further comprising determining a subset k with a least power consumption for a required load based on an approximated power consumption P=f(q, .sub.j) and/or the approximated pump characteristic p=f(q, .sub.j) stored in the storage module.

19. The method according to claim 18, further comprising operating the multi-pump system with the determined subset k having the least power consumption for a required load.

20. The method according to claim 14, further comprising running the i pumps of a subset j with the same speed .sub.j during a configuration cycle j, wherein the speed .sub.j of the i pumps of subset j in configuration cycle j differs from the speed .sub.k of s pumps of a subset k in another configuration cycle k, wherein js, wherein a total head p generated by the multi-pump system is substantially the same for both configuration cycles j, k.

21. The method according to claim 14, further comprising determining the approximated pump characteristic p=f(q, .sub.j) by determining parameters a, b and c of a second order polynomial $p (q,_{j}) = {a (\frac{q}{i})}^{2} + b (\frac{q}{i})_{j} + c_{j}^{2},$ wherein .sub.j is the speed of the i pumps of a subset j.

22. The method according to claim 14, further comprising: running a zero flow configuration cycle by ramping up the speed of at least one pump in addition to a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump starting to contribute to a total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-up pump in the moment it starts to contribute to the total flow; or running a zero flow configuration cycle by ramping down the speed of at least one pump of a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump stopping to contribute to the total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-down pump in the moment it stops to contribute to the total flow; or running a zero flow configuration cycle by ramping up the speed of at least one pump in addition to a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump starting to contribute to the total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-up pump in the moment it starts to contribute to the total flow; and running a zero flow configuration cycle by ramping down the speed of at least one pump of a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump stopping to contribute to the total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-down pump in the moment it stops to contribute to the total flow; and further comprising identifying the received signal change by using a change detection algorithm.

23. The method according to claim 14, further comprising: running a zero flow configuration cycle by ramping up the speed of at least one pump in addition to a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump starting to contribute to a total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-up pump in the moment it starts to contribute to the total flow; or running a zero flow configuration cycle by ramping down the speed of at least one pump of a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump stopping to contribute to the total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-down pump in the moment it stops to contribute to the total flow; or running a zero flow configuration cycle by ramping up the speed of at least one pump in addition to a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump starting to contribute to the total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-up pump in the moment it starts to contribute to the total flow; and running a zero flow configuration cycle by ramping down the speed of at least one pump of a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the at least one pump stopping to contribute to the total flow, and wherein the processing module is configured to determine an approximated pump characteristic p.sub.0.sup.2 and/or power consumption P.sub.0.sup.3, wherein .sub.0 is the speed of the at least one ramped-down pump in the moment it stops to contribute to the total flow; and further comprising identifying the received signal change by determining if an absolute value of the gradient in p, speed .sub.j, and/or power consumption P is equal to or exceeds a pre-determined threshold value.

24. The method according to claim 14, further comprising: ramping up the speed of k pumps in addition to a subset j of i pumps of a multi-pump system comprising N pumps and running at a speed .sub.j providing a total head p, wherein N2, 1k<N and 1i<N; and ramping down the i pumps of the subset j from the speed .sub.j to a lower speed .sub.m, wherein the speed .sub.m is the speed required for a subset m of i+k pumps to provide the total head p; or ramping down the speed of k pumps of a subset j of i pumps of a multi-pump system comprising N pumps and running at a speed .sub.j providing a total head p, wherein N2, 1k<i and 1<iN, and ramping up the i-k pumps of a residual subset r from the speed .sub.j to a higher speed .sub.r, wherein the speed .sub.r is the speed required for a residual subset r of i-k pumps to provide the total head p; or ramping up the speed of k pumps in addition to a subset j of i pumps of a multi-pump system comprising N pumps and running at a speed .sub.j providing a total head p, wherein N2, 1k<N and 1i<N; and ramping down the i pumps of the subset j from the speed .sub.j to a lower speed .sub.m, wherein the speed .sub.m is the speed required for a subset m of i+k pumps to provide the total head p and ramping down the speed of k pumps of a subset j of i pumps of a multi-pump system comprising N pumps and running at a speed .sub.j providing a total head p, wherein N2, 1k<i and 1<iN, and ramping up the i-k pumps of a residual subset r from the speed .sub.j to a higher speed .sub.r, wherein the speed .sub.r is the speed required for a residual subset r of i-k pumps to provide the total head p.

25. The method according to claim 24, further comprising keeping the total head p constant while ramping up or while ramping down.

26. The method according to claim 24, wherein the ramping up or the ramping down follows at least one pre-determined model curve.

27. The method according to claim 14, wherein a computer readable non-transitory medium is provided with instructions for executing the method steps.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present disclosure will now be described by way of example with reference to the following figures of which:

(2) FIG. 1 is a schematic view showing a fluid supply network supplied by a multi-pump system controlled by an example of a multi-pump control system according to the present disclosure;

(3) FIG. 2 is a diagram of an approximated pump characteristic;

(4) FIG. 3 is a diagram of an approximated power consumption;

(5) FIG. 4 is a diagram of the pump speed during ramp-up of an additional pump when a subset of pumps is already running;

(6) FIG. 5 is a diagram of the total head during ramp-up of an additional pump when a subset of pumps is already running;

(7) FIG. 6 is a diagram of the speed during an optimized ramp-up of an additional pump and ramp-down of an already running subset of pumps; and

(8) FIG. 7 is a flow diagram of an example of the method according to the present disclosure.

DETAILED DESCRIPTION

(9) FIG. 1 shows a fluid network 1 supplied by a multi-pump system 3 of four pumps 3a, 3b, 3c, 3d. The fluid network 1 may, for instance, be a heating or cooling cycle. The fluid network 1 does not need to be a closed loop cycle. It may comprise two reservoirs, wherein the multi-pump system 3 is installed to pump fluid, e.g. water, from one reservoir to the other. In this example, the pumps 3a, 3b, 3c, 3d of the multi-pump system 3 are installed in parallel. The pumps 3a, 3b, 3c, 3d of this example are also of nominally the same type and size.

(10) A multi-pump control system 5, comprising a control module 7, a processing module 9, communication interface 11, and a storage module 13, is in direct or indirect, wireless or wired communication connection with the pumps 3a, 3b, 3c, 3d. The communication interface 11 comprises one or more processor (C, P, DSP) and one or more transmitter/receiver with the communication interface 11 configured to send signals to and receive signals from the pumps 3a, 3b, 3c, 3d. The processing module 9 comprises one or more processor and is configured to process received signals and to execute calculations based on the received signals. The storage module 13 comprises one or more memory unit cooperating with one or more processor and is configured to store the results of the calculations. The control module 7 comprises one or more processor and is configured to control the pump operation based on the stored results by commands via the communication interface 11 to the pumps 3a, 3b, 3c, 3d. It should be noted that the control module 7, the processing module 9, the communication interface 11, and the storage module 13 may be physically distributed over the system 5 which does not have to be physically comprised within a single unit. Two or more of the modules may be combined (with common or non-common processor or processors), so that the functionality of more than one module is provided by a combined module.

(11) For instance, the multi-pump control system 5 may constantly, regularly or sporadically check if a currently running subset of pumps is the most energy efficient operating mode to provide a required total flow q and a required total head p to the fluid network 1. The required total flow q and the required total head p may be summarized by a required total load. For example, the four pumps 3a, 3b, 3c, 3d may be able to provide a certain maximum load, of which only 75% is currently required by the fluid network 1. The multi-pump control system 5 may thus run three pumps at maximum speed having four options which of the pumps to shut down, e.g. 3d. Another option would be to run all four pumps 3a, 3b, 3c, 3d at 75% of their maximum speed. Assuming that all pumps of a running subset should run at the same speed, the multi-pump control system 5 has now five options which all may show different power consumptions.

(12) However, running the system most energy-efficiently is not a trivial task if there is no flow measurement available and the current pump characteristics are unknown. For instance, the pump characteristics may not be given if the multi-pump control system 5 is retro-fitted to an already installed multi-pump system 3. Even if they were originally known, they could show unknown manufacturing variances, or may have changed over time due to degradations, wear, or fouling. The trick is thus to identify the most energy-efficient subset for a required load in lack of information on the current flow and the current pump characteristics.

(13) In order to approximate the pump characteristics, the control module 7 is configured to run a certain number, i.e. n, of different configuration cycles. Each configuration cycle may be labeled with the index j. Each configuration cycle is run with a different subset of the pumps 3a, 3b, 3c, 3d. As the subset should change between the configuration cycles to gain information, each subset may be labeled with the same index j. With N=4 being the total number of pumps in the multi-pump system 3 and i as the number of pumps in the subset j, the following conditions apply: N2, 2n2.sup.N1 and 1iN. During each configuration cycle, the i pumps of the subset j are run at the same constant speed .sub.j. The speed is adapted between the configuration cycles to maintain the same total head, i.e. pressure differential p. The measured and monitored pressure differential p.sub.j and the recorded speed .sub.j is communicated to the control module 7 by the communication interface 11, which is configured to receive signals indicative of operational parameters from each subset j during the associated configuration cycle j. The processing module is configured to determine an approximated pump characteristic in form of a second order polynomial

(14) $p_{j} (q,_{j}) = {a (\frac{q}{i})}^{2} + b (\frac{q}{i})_{j} + c_{j}^{2}$
based on the assumption that the i pumps of each subset j share the same part q/i of a reference flow q. The reference flow q may be a measured or a normalized value, i.e. it may be arbitrarily set to q=1. The storage module is configured to store the approximated pump characteristic or the parameters indicative thereof, i.e. a, b and c.

(15) Furthermore, in each configuration cycle the power consumption P.sub.j=f(q, .sub.j) is approximated by a second order polynomial

(16) 0 $P_{j} (q,_{j}) = {x (\frac{q}{i})}^{2}_{j} + y (\frac{q}{i})_{j}^{2} + z_{j}^{3}$
based on the assumption that the i pumps of each subset j share the same part q/i of a reference flow q. The parameters x, y and z are parameters indicative of the power consumption and stored in the storage module.

(17) Thus, the six parameters a, b, c, x, y, and z can be determined from the six equations yielded by three configuration cycles with subsets of a different number of pumps. So, preferably, the number of running pumps i should change between the cycles. If the multi-pump system comprises only two pumps, i.e. N=2, a zero flow configuration cycle (further explained below) may be used to pre-determine the parameters c and z, so that the remaining four parameters are well determined by the four equations yielded by running a first configuration cycle with one pump and a second cycle with two pumps.

(18) The following table may illustrate the options of running configuration cycles for the system 3 of four pumps 3a, 3b, 3c, 3d as shown in FIG. 1. The status of all pumps is illustrated by a binary number with N=4 bits, where each bit represents a pump, i.e. 0 means off, 1 means on, and the binary weight represents the number i of pumps in the running subset j:

(19) TABLE-US-00002 Number of pumps Configuration Subset, in running subset, Status of all N = 4 pumps; cycle, i.e. j i.e. j i.e. i 0 is off, 1 is on 1 1 1 0001 or 0010 or 0100 or 1000 2 2 2 0011 or 0101 or 0110 or 1100 or 1001 or 1010 3 3 3 1110 or 1101 or 1011 or 0111 4 4 4 1111

(20) Running more than three configuration cycles will over-determine the parameter set. The total number of permutations for running subsets is 2.sup.N1, i.e. in this case 2.sup.41=15. In order to take differences between pumps into account caused by manufacturing tolerances, wear or fouling, more than three configuration cycles allow an averaging over the pumps. Thereby, the approximation may be closer to the real pump characteristics of the pump system.

(21) The simple case of running three configuration cycles, e.g. the first cycle (j=1) with one (i=1) pump, the second cycle (j=2) with two (i=2) pumps and the third cycle (j=3) with three (i=3) pumps, may be implemented as an algorithm (here as a c-style meta language) as follows:

(22) TABLE-US-00003 for (j=1; j<4; j++){ i=j; if (i==1){ Run pump #1 at 95% speed; Assign q=1; Record p.sub.j, .sub.j, P.sub.j, q.sub.j; p= p.sub.j; } else if (i==2) { Run pumps #1 and #2; Regulate .sub.j to set p.sub.j= p; Assign q.sub.j=1/i; Record p.sub.j, .sub.j, P.sub.j, q.sub.j; } else { Run pumps #1, #2 and #3; Regulate .sub.j to set p.sub.j= p; Assign q.sub.j=1/i; Record p.sub.j, .sub.j, P.sub.j, q.sub.j; } }

(23) More than three configuration cycles may be implemented as an algorithm (here as a c-style meta language) as follows:

(24) TABLE-US-00004 k=1; // run over all possible permutations of subsets j for (j=1; j<2.sup.N; j++){ if (k=1){ Run pump #1 at 95% speed; Assign q=1; Record p.sub.j, .sub.j, P.sub.j, q.sub.j; p= p.sub.j; k=2; } else // determine i of subset j by counting 1-bits x=j; i=0; while (x1) { // mod(2) adds 1 if x is odd, 0 if x is even i+=x%2; x = floor(x/2); } // only run subsets of three pumps if (i3){ // Run pump(s) according to the 1-bits of j x=j; bit =1; while (x1) { if(x%2==1) { Run pump #bit; } x = floor(x/2); bit++; } Regulate .sub.j to set p.sub.j= p; Assign q=1/i; Record p.sub.j, .sub.j, P.sub.j, q.sub.j; } } }

(25) In the above example for N=4 pumps, the algorithm would produce four cycles with one pump, six cycles with two pumps and four cycles with three pumps, i.e. in sum 14 cycles. A least squares method can be used to find average values for the parameters a, b c, x, y and z. Furthermore, outliers may be determined during redundant configuration cycles in order to neglect those in the averaging and/or to identify and ban low efficiency pumps of the multi-pump system 3. Such identified low efficiency pumps may be indicated for service, repair or replacement. It is preferred to run only subsets of three pumps, because cycles with subsets of many pumps only differ marginally from cycles with subsets of one more or less pump. In principle, however, the configuration cycles can be run with any number of pumps iN.

(26) FIGS. 2 and 3 show the resulting polynomial approximations as a dashed line. In some cases, as shown by the dashed lines, the approximated polynomials may not be accurate in certain areas. For instance, the dashed lines predict negative power consumption at very low flow, which is obviously not correct. This can be improved by running a zero configuration cycle as explained in the following.

(27) Before a zero flow configuration cycle of the multi-pump system 3 with the four pumps 3a, 3b, 3c, and 3d, only a subset of three pumps 3a, 3b and 3c may be running at a speed .sub.j while pump 3d is not running. During the zero flow configuration cycle, pump 3d is ramped-up in speed. As long as the pressure differential provided by the current speed of pump 3d is below the total head p, pump 3d does not contribute to the total flow. Once the communication interface 13 receives a signal change indicative of the at least one pump starting to contribute to the total flow, the current speed .sub.0 of pump 3d is recorded in the moment the pump 3d starts to contribute to the total flow. The parameter c can then be determined from p=c.sub.0.sup.2. The parameter c determined in the zero flow configuration cycle may be used to improve the polynomial approximations as shown by solid lines in FIGS. 2 and 3. As can be seen, there is no prediction of negative power consumption at low flow. The power consumption usually follows a slight S-shape which is usually better approximated by a third-order polynomial. However, the comparison with a third-order polynomial for approximating the power consumption in FIG. 3 (dashed-dotted line) shows that the overall prediction of the second-order approximation (solid) is quite good up to the maximum power consumption at about 100 m.sup.3/h after correction by the zero flow configuration.

(28) FIGS. 4 and 5 show the sudden signal change for the speed (FIG. 3) and the pressure (FIG. 5) when the added pump 3d starts contributing to the flow. At the start of the ramp-up phase, the three running pumps 3a, 3b, 3c run constantly at about 80% of their maximum speed and provide all the flow. Pump 3d is linearly ramped-up at about 20% of the maximum speed per 25 seconds. When the speed .sub.0 at about 40% of the maximum speed is reached after about 57 seconds, the pressure differential of pump 3d equals the total head p and pump 3d suddenly starts contributing to the flow. The control module 7 reacts immediately to keep the total head p constant by reducing the speed of the running pumps 3a, 3b, 3c to about 40% of the maximum speed. The system may then converge towards a common speed of the new subset with i+1 pumps, i.e. of all four pumps, providing the same total head p at about 40% of the maximum speed. However, the point when the added pump actively joins in, the sudden signal change shows as a disturbance in form of a spike (15) in pressure and a steep drop (17) in speed. A CUSUM algorithm can be used to detect this sudden signal change.

(29) Optionally, the total head and/or flow may be held essentially constant during the ramping up/down of the at least one pump as shown in FIG. 5. In option a), i.e. when at least one pump is ramped up in addition to an already running subset j, the subset j may provide an essentially constant pressure and the ramped-up pump does not contribute to the flow until the speed .sub.0 is reached, which is just sufficient to provide that constant pressure. Analogously, in option b) (not shown), i.e. when at least one pump of a running subset j is ramped down, the subset j may provide an essentially constant pressure and the ramped-down pump still contributes to the flow until its speed falls below the speed .sub.0 which is at least necessary to provide that constant pressure. In both cases, this causes a sudden signal change that may show as a spike or steep drop in a diagram in which the speed, the pressure or the power consumption is recorded over the ramping time.

(30) Optionally, the received signal change is identified by determining if the absolute value of the gradient in head p, speed .sub.j, and/or power consumption P is equal to or exceeds a pre-determined threshold value. Optionally, a change detection algorithm, for instance a cumulative sum (CUSUM) algorithm, is used for identifying the received signal change.

(31) A CUSUM algorithm is particularly useful for detecting changes in the mean value of a signal. For instance, in view of a signal diagram over time, wherein the speed, the pressure or the power consumption is the signal, the positive and negative signal differences from its mean may be summed up to a monitored quantity. If the monitored quantity is equal to or exceeds a certain threshold, the mean value can be interpreted to have changed. Alternatively or in addition, the absolute value of the gradient in head p, speed .sub.j, and/or power consumption P may be measured and compared with a pre-determined threshold value. If the threshold value is reached or exceeded, the sudden signal change is indicative of the at least one pump starting to contribute to the total flow.

(32) The disturbance is useful in the zero configuration cycle, but not desired for the normal pump operation when, for instance, the control unit decides that the system would consume less power with an additional pump, and therefore ramps up another pump. In this normal operation, optionally, the control module may be configured to ramp up the speed of the pump 3d in addition to the subset of the three pumps 3a, 3b, 3c running at speed .sub.j providing a total head p, and simultaneously to ramp down the three pumps 3a, 3b, 3c from the speed .sub.j to a lower speed .sub.m, wherein the speed .sub.m is the speed required for the new subset of four pumps to provide the total head p. Such a simultaneous convergence of speeds is shown in FIG. 6, where the parameter ranges from 0 (start of the ramping) and 1 (end of the ramping). The disturbance, as it is shown in FIGS. 4 and 5 for the zero flow configuration cycles, will be significantly reduced, because the running subset of three pumps 3a, 3b, 3c is already at the final speed .sub.m, when the fourth pump 3d joins in contributing flow at the same speed .sub.m. As any disturbance represents an energy-inefficiency, this simultaneous convergence saves power and may be referred to as a smooth cutting in/out of pumps. The total head p and/or the total flow are kept essentially constant during the ramping for all values of .

(33) Knowledge of the speed .sub.0 and the approximated power consumption P=f(q, .sub.j) and/or the approximated pump characteristic p=f(q, .sub.j) may allow for the control module to ramp up/down following at least one pre-determined model curve. Thereby, the time for convergence after the added pumps actively joins in contributing flow can be significantly reduced, because the final speed .sub.m can be predicted. Following the pre-determined model curve may automatically result in a constant total head p and/or the total flow for all values of . Therefore, no feedback-loop for controlling based on monitored measured values may be needed.

(34) If one or more pumps of a running subset are ramped down, the way back from parameter at a value of 1 (start of the ramping) to 0 (end of the ramping) follows analogously. Similarly, also the zero flow configuration cycles may be run by ramping one or more pumps of a running subset down and recording the speed at which the ramped-down pump(s) suddenly stop contributing to the total flow.

(35) FIG. 7 shows an example of method steps in some subsequent order. However, the method may be implemented in a different order of steps, or the method steps may be repeated or executed in parallel to other method steps. In FIG. 7, a zero flow configuration cycle is run (701) by ramping up (703a) the speed of one pump in addition to a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the pump starting to contribute to the total flow, and determining (705a) an approximated pump characteristic p=c.sub.0.sup.2 and power consumption P=z.sub.0.sup.3, wherein .sub.0 is the speed of the ramped-up pump in the moment it starts to contribute to the total flow. Alternatively or in addition, the zero flow configuration cycle is run (701) by ramping down (703b) the speed of one pump of a subset j of i pumps of a multi-pump system running at a speed .sub.j until the communication interface receives a signal change indicative of the pump stopping to contribute to the total flow, and determining (705b) an approximated pump characteristic p=c.sub.0.sup.2 and power consumption P=z.sub.0.sup.3, wherein .sub.0 is the speed of the ramped-down pump in the moment it stops to contribute to the total flow.

(36) The method as shown in FIG. 7 further comprises running (707) n different configuration cycles with subsets of i pumps running at a speed .sub.j. During each configuration cycle j, signals indicative of operational parameters are received (709) from the running subset j. The method further comprises determining (711a) an approximated pump characteristic

(37) $p_{j} (q,_{j}) = {a (\frac{q_{j}}{i})}^{2} + b (\frac{q_{j}}{i})_{j} + c_{j}^{2}$
and determining (711b) a power consumption

(38) $P_{j} (q,_{j}) = {x (\frac{q}{i})}^{2}_{j} + y (\frac{q}{i})_{j}^{2} + z_{j}^{3}$
based on the received signals and under the assumption that the i pumps of each subset j share the same part q/i of a reference flow q. The pump characteristic (or parameters a, b and c indicative thereof) and the power consumption (or parameters x, y, and z indicative thereof) are then stored (713).

(39) A subset k with the least power consumption for a required load is then determined (715) based on the approximated power consumption and/or the approximated pump characteristic stored in the storage module 13. The multi-pump system is then operated (717) by the determined subset k having the least power consumption for a required load. When it is energetically more efficient to change the running subset to i+1 or i1 pumps, another pump may be smoothly cut in/out (719) by either: ramping up (721a) the speed of a pump in addition to a subset j of i pumps running at a speed .sub.j providing a total head p, and ramping down (723a) the i pumps of the subset j from the speed .sub.j to a lower speed .sub.m, wherein the speed .sub.m is the speed required for a subset m of i+1 pumps to provide the total head p; or ramping down (721b) the speed of a pump of a subset j of i pumps running at a speed .sub.j providing a total head p, and ramping up (723b) the i1 pumps of a residual subset r from the speed .sub.j to a higher speed .sub.r, wherein the speed .sub.r is the speed required for a residual subset r of i1 pumps to provide the total head p.

(40) Where, in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that are described as optional, preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

(41) The above embodiments are to be understood as illustrative examples of the disclosure. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. While at least one exemplary embodiment has been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art and may be changed without departing from the scope of the subject matter described herein, and this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

(42) In addition, comprising does not exclude other elements or steps, and a or one does not exclude a plural number. Furthermore, characteristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combination with other characteristics or steps of other exemplary embodiments described above. Method steps may be applied in any order or in parallel or may constitute a part or a more detailed version of another method step. It should be understood that there should be embodied within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of the contribution to the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the disclosure, which should be determined from the appended claims and their legal equivalents.

(43) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

Multi-pump control system with power consumption optimization

Assignee

Inventors

Cpc classification

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F04D15/0066

MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

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E03B5/00

FIXED CONSTRUCTIONS

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F04D15/029

MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

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F04D13/14

MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

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F04D1/04

MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

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G05B15/02

PHYSICS

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G06F17/14

PHYSICS

International classification

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F04D15/00

MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

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G06F17/14

PHYSICS

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G05B15/02

PHYSICS

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F04D1/04

MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

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F04D13/14

MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

Classification Explorer

F04D15/02

MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING

Abstract

Claims

Description